Let's begin 2016 with thrilling sound of our first H-bomb: Kim Jong-un before North Korea’s test

Seoul: North Korean leader Kim Jong-Un personally signed the order three weeks ago authorising Pyongyang's latest nuclear test, calling for 2016 to kick off with the "thrilling sound" of a hydrogen bomb explosion.

The North said on Wednesday it had conducted its first "successful" miniaturised hydrogen bomb test -- a shock announcement that drew condemnation from its neighbours including its major ally China.

The news was broadcast on state television, which also showed a copy of Kim's initial signed order dated 15 December.

"Let's begin the year of 2016 ... with the thrilling sound of our first hydrogen bomb explosion, so that the whole world will look up to our socialist, nuclear-armed republic and the great Workers' Party of Korea!" Kim wrote in a handwritten message next to his signature.

The television also showed a second order dated 3 January in which Kim signed off his final approval for the test to be conducted on 6 January.

Kim, who took over after the death of his father Kim Jong-Il in December 2011, also presided over the country's third nuclear test in February 2013.

A hydrogen, or thermonuclear, bomb uses fusion in a chain reaction that results in a far more powerful explosion than the fission blast generated by uranium or plutonium alone.

North Korea was believed to be years from developing such a sophisticated device, and experts voiced scepticism that Wednesday's test was indeed of a hydrogen bomb -- saying the apparent yield was far too low.

Kim had suggested last month Pyongyang had already developed such an H-bomb -- a claim that was largely dismissed as exaggerated rhetoric at the time.